The Magellanic Stream (MS) is a prominent local example of a gaseous galactic halo remnant. Spanning the Southern Galactic sky behind the Magellanic Clouds, it presents a nearby laboratory with which to study the fate of cool gas streams injected into a galactic environment, considered possible fuel sources for sustained star formation. We present results based on 21 cm observations on the MS from the Green Bank Telescope (GBT) that, through special data reduction, averaging and 3D modeling techniques, reach more than five times the sensitivity of existing maps while essentially retaining the 9' base GBT resolution. This provides a crude, but unprecedented peek into the 3D structure and kinematics of the diffuse neutral component that traces the warm, highly ionized MS-to-Halo transition layer. Previously, this has been probed only through a small number of optical and UV metal absorption sight lines. Understanding the ablation process mediated by this layer as the gas works its way through the halo at high shear velocities is crucial in evaluating the potential for intruding gas to reach a galaxy disk. Under these conditions, hydrodynamic instabilities such as Rayleigh-Taylor can operate on small scales, creating a complex thermal and kinematic environment, strongly influencing the overall mass transfer rate and, therefore the lifetime of the injected cool gas. A turbulent mixing layer is generally pictured as a strong candidate for this interface and we show how the results fit into that picture.